1. Field of the Invention
The invention relates to digital broadcasts, and more particularly to receiving digital broadcasts.
2. Description of the Related Art
Digital television can provide better video quality and audio quality. It can also provide value-added services derived from digital television broadcasts. Because the value-added services bring great profits, enterprises in advanced countries are competing to develop business in this field, and the television broadcasts is gradually being transformed from traditional analog systems to digital systems. If television signals are broadcasted from traditional analog systems, the signal strength tends to be subject to the landforms in the transmission path, but the television signals broadcast from digital systems are not interfered with by the landforms in the transmission path. Additionally, bandwidth utilization of digital broadcasting is more efficient than that of analog broadcasting. Most importantly, digital broadcasts can provide a variety of value-added services derived from data broadcasting.
The digital broadcast signal-transmission mediums include cable, satellite, microwave, and terrestrial. The current digital terrestrial television broadcasting (DTTB) standard includes the Advanced Television System Committee (ATSC) standard of the United States, the Digital Video Broadcasting-Terrestrial (DVB-T) standard of Europe, and the Integrated Services Digital Broadcasting-Terrestrial (ISDB-T) standard of Japan. The DVB-T standard was accepted by European Telecommunication Standard Institute (ETSI) in February 1997 as the digital terrestrial television broadcasting standard of Europe (ETS 300 744). Australia, New Zealand, Singapore and Taiwan have also adopted the DVB-T standard for DTTB.
Current DVB-T players provide an auto scan function for automatically scanning and setting DVB-T broadcast channels. The scanning mode of the auto scan function includes “all channel scan” for scanning the whole frequency band for all channels in the region, “frequency range scan” for scanning a frequency range for channels, and “programmable user channel” for scanning a single channel set by a user. The mentioned scanning modes scan all channels sequentially through a range of frequency band. Scanning a single channel, however, requires one or two minutes (the bandwidth of a single channel is about 6 MHz), and the time required to scan the entire frequency band depends on the scan range of the frequency band and is about several to ten minutes. This increased time required causes large power consumption when the DVB-T receiver is installed in a notebook computer as the available power is limited. Additionally, if parameters for receiving a channel are not correct and cause errors, the parameters cannot be automatically adjusted, causing further inconveniences.